1. Technical Field of the Invention
This disclosure relates generally to a rotating internal gear pump, such as a trochoid pump, which works to suck fluid and discharge it and a brake system using such a type of pump.
2. Background Art
Typical rotating internal gear pumps are equipped with an inner rotor with outer teeth, an outer rotor with inner teeth, and a casing including side plates and a center plate. The inner rotor and the outer rotor are disposed inside the casing. The outer teeth of the inner rotor mesh with the inner teeth of the outer rotor to form a plurality of cavities which vary in volume thereof with rotation of the inner and outer rotors to pump out fluid.
The above type of pumps are required to hermetically isolate between a high-pressure region and a low-pressure region within the pumps. Such hermetic isolation is achieved by pressing a sealing member installed in one of the side plates against one of opposed major end surfaces of each of the inner and outer rotors and also pressing the other major end surface of each of the inner and outer rotor directly against the other side plate to create a mechanical seal therebetween. Additionally, a sealing member is mounted in a recess formed in the center plate and urged against an outer circumferential wall of the outer rotor to develop a hermetic seal therebetween.
The mechanical seal between the side plate and each of the outer and inner rotor results in an increase in loss of torque of the outer and inner rotors, which results in production of heat, thus thermally expanding a portion of the pump to deteriorate the performance of the pump.
In order to eliminate the above drawback, Japanese Patent First Publication No. 2004-176676 teaches a rotating pump for an automotive vehicles which has a protrusion formed on a central area of an end surface of the side plate (i.e., a pump cover) which is placed in line contact with each of the inner and outer rotors to create a mechanical seal therebetween, thereby minimizing the amount of heat, as produced by friction between the side plate and each of the inner and outer rotors.
Specifically, a portion of the end surface of the side plate which faces the inner and outer rotors is entirely inclined to form a gap between itself and each of the inner and outer rotors. The brake fluid is accumulated in the gap to reduce friction resistance to sliding motion of each of the inner and outer rotors on the side plate, however, it results in concern about leakage of the brake fluid from a high-pressure region to a low-pressure region in the pump.